The present invention relates to improvements in a mold for forming golf balls.
In general, metallic molds for injection molding operation or for pressing operation or other similar molds are used to mold golf balls. In such conventional metallic molds, hold pins, vent pins, ejector pins and the like are employed. This kind of well known metallic molds are such as shown in FIG. 4 of the accompanying drawings and as described in U.S. Pat. No. 5,122,046.
A metallic mold 100 depicted in FIG. 4 of the accompanying drawing is fitted with pins, or hold pins 101 such that they can be reciprocated. The hold pins 101 are located in the metallic mold such as to coincide with the positions of dimples made in a golf ball intended to be manufactured by using the metallic mold 100, and the hold pins 101 form dimples in the golf ball by means of their head portions 102. The head portions 102 of the hold pins 101 are curved as shown in FIG. 5A of the accompanying drawings by electrospark machining operation, engraving or other similar means.
However, as viewed from the center O of the cavity which is shown in the metallic mold in FIG. 4, the head portions 102 of the hold pins 101 respectively look elliptical as shown in FIG. 5B. It follows from this that the dimples formed by using the head portions 102 of the hold pins 101 are also elliptical in their configurations.
The dimples made by means of the head portions 102 are thus uncircular in their configurations unlike other dimples formed without the use of the head portions 102. For this reason, golf balls molded by using the conventional molds are bad in their external appearances, while at the same time, they are inferior in their flying performance.
Also, in a metallic mold disclosed for golf balls in U.S. Pat. No. 5,122,046, a hold pin used therein is hemispherical in the configuration of the head portion thereof. Therefore, this mold undergoes the following problems.
(i) The hold pins forms in an elliptical configuration the dimples of the golf balls produced by using this mold. PA0 (ii) The dimples of the golf balls are not directed in their axes to the centers of the golf balls. PA0 (iii) Therefore, the golf ball thus obtained are bad in their external appearances, while at the same time, they are inferior in their flying performance.
It is therefore an object of the present invention to provide for dimples of the same configuration in golf balls intended to be molded by using the metallic mold according to the present invention, whereby the golf balls are improved in their external appearances.
Also, it is another object of the present invention to provide for molding of golf balls which are superior in their flying performance.